When servicing your coolant system, this convenient billet aluminum plug serves to prevent coolant leakage from the engine oil cooler adapter.For instance, when installing PPE exhaust manifolds and up-pipes on a 2007.5-2010 GM 6.6L Duramax LMM, the original coolant tube becomes incompatible. Consequently, the coolant reroute tube must be removed and replaced. In this process, our coolant block off plug serves as a temporary solution, halting coolant leakage from the engine oil cooler adapter dur